If you, like many other people, are looking for ways to save money by looking outside your normal vendors’ offerings, one way is to understand what other products are out there and how they relate to your requirements.
The first rule is to have a clear, defended statement of requirements (and if you do not have network documentation, this is a great time to do that NOW). This is the tricky part, really.
If you are adding network equipment to your existing infrastructure, then you must know what it is using (what standards of the many Ethernet standards). For example, if you are using a form of spanning-tree on your network, then you must look at your existing kit and see what flavour of spanning tree you are running. You could be running STP, RSTP, MSTP or PVST+.
Once you build up a list of what standards or protocols (features) you use in your network, you have to map these to their IEEE/RFC standards/comments name and identify if you are using any proprietary vendor features. 802.1D (case in these IEEE standards is important, so please note that this is a upper case ‘D’) equals MSTP. However, that is the original and has been surpassed by IEEE 802.1D-2004 – this incorporates 802.1w (rapid spanning-tree).
Then the work of comparing hardware can have a positive outcome in a $$$ sense that still meets the requirements – without the surprises down the road (What? I bought this switch only 6 months ago, and you say it only does IPv6 for management!!!).
Example again, if you do have a vendor proprietary feature, how long will it take you to transition it to a standards-based protocol? Is that time worth more to you then the added cost of new equipment from another vendor? Also, what did the vendor feature offer that is better (or worse) then the standard? Only you can work this one out – it is your network!
Now we get down to the reading and understanding of datasheets – the fun part.
There are mostly two types of datasheets – ‘Marketing Edited’ and ‘Just the Facts’ with a good amount of gray in between.
Rule 1 – Marketing will not allow any fact that says we are worse then the competition. (Ask yourself why Cisco does not put latency figures on their datasheets and why Arista Networks does.)
Rule 2 – The top half of the datasheet is all marketing.
Rule 3 – The tables and compliance lists – this is where you get the real information you need.
Right – now that the rules are out of the way, what is there to look for on a datasheet?
- Wire speed – This means that all ports can run at full speed; e.g. not oversubscribed.
- Forwarding throughput – How much data can be moved.
- How many ports – be careful with the words “combo ports”. Say on a 24 port switch with 4 combo ports, how many ports can I use? The answer is 24, not 28.
- Power/Watts per port – Time for everyone to take into account the power consumption – the lower, the better.
- Understand what the warranty is and what is included – you may not need a support contract, so look closely and decide.
- If looking at PoE+ switches, make sure it provides enough power – some 48 port PoE+ switches only deliver enough PoE+ power to drive 24 ports of PoE+ – once the power budget is consumed, the rest of the ports are non-PoE ports.
- NOISE – Often overlooked, this one. If you plan to put a switch in an office space, PLEASE check the noise rating. Datacentre switches do not make good office switches.
- IPv6 – As the world crawls towards IPv6, make sure you check the performance of IPv6 vs IPv4 – lots of boxes do IPv6 REALLY badly.
What’s normally missing in datasheets:
- Latency – Not just the realm of the traders, low latency can make a good iSCSI setup great.
- Buffers – fan in and fan outs – going from a 10G port into a 1G port is where buffers are needed.
- Port groups – when port groups are used in a switch, latency will be affected (much higher) – ask what the worst case is.
Hopefully, this gives you some useful knowledge, but remember that if you are not confident in choosing your own gear, select a trusted VAR or contractor to do it. You do not want to be stuck with kit that does not meet the requirements for ‘x’ years until the boss agrees to upgrade again.